Space Invaders
by natis1
Summary: In a semi-canon post Legacy of the Void world, a band of independent zerg scientists set out to explore the terran home world, interested in what other life inhabited it. What happened to the planet? How do zerg go about stealing genes? And how does an independent Zerg view the creatures of Earth anyway? The first chapter is pretty dry.


Why venture towards the Terran home world? Most zerg wanted nothing to do with those aliens. As best the leviathan, and her members could tell, the place was still under the dominion of the United Earth Directorate (or perhaps dictatorship would be a more accurate word). Although they had only fought this empire once, zerg generally shared a collective hatred of them and their planet. It wasn't that their armies tried to take over the Overmind, few even remember the being. It was mostly Kerrigan. This new age of zerg had grown to resent everything about her—including her species. Zerg would sooner want to infest the grass than a Terran. No wonder that the moment the Zerg regained their autonomy infestors had given up growing them. Yet, for a few zerg, this hatred was outweighed by a sense of curiosity. They wondered what other life could possibly exist on a homeworld capable of harboring creatures that could conquer and control them for almost a decade.

100 AUs away from the planet and a nervous tension spread throughout the ship. Jonah shared in these collective thoughts as he watched the leviathan exit hyperspace and the dust and light of the star faded into view through the cellophane windows. "Sora?" he asked the leviathan, speaking to her telepathically, the way all zerg communicated. "I think we should try to stay a little bit back and scan the planet. I...I'm a little scared. I'd hate to get found out and obliterated by their awful weapons before we have a chance to run away."

"Fully agree." The leviathan spoke back, and Jonah sensed this sentiment among the others. Her floor seemed to vibrate a little as her mind-energies rippled into Jonah's spiny body. "We should scan it from here, and when we're certain they'll make it, maybe at the most send a small pod to investigate it. I'd hate for us all to die just because we were caught. Who knows what Xel-forsaken machinery they have to cut through us?" And with that, Sora came to a complete stop, hidden among the rocks of the Kuiper belt. She telepathically signaled to the bio team who scrambled through the protein archives before finding the right one, and handing it to her, or more accurately, pouring it onto her. Sora began growing a thin film over her body—It bent light towards her windows which the excited zerglings from communications and systems rushed over to investigate.

While Jonah was busy admiring the outside world, which had suddenly grown quite bright from the lensing proteins, a consensus had formed among the others. Something was quite wrong; there were a couple of Terran ships orbiting the sun but they all seemed inactive. They couldn't easily see through the Earth's atmosphere, but there definitely wasn't any artificial light coming from the planet's moon. At first Sora and the others suspected it was a trap, but after inspecting other frequencies and not finding any radio or microwave signals they decided to move a little closer. After all, how else could those creatures communicate?

10 AUs away from the planet, and still nothing seemed to react to their presence. The artificial satellites which orbited Jupiter and Saturn had decayed into an eccentric elliptical orbit, and seemed destined to be crushed by the gas giants in just a few decades. Thermal signatures, or rather lack thereof, indicated to the leviathan and its crew that their RTGs were no longer functional, and the satellites had run out of energy. Surely terrans wouldn't sacrifice such expensive vessels merely as a trap, thought the hive mind. This helped inspire the confidence in Sora to attempt an orbit around Terra. She gracefully glided between the asteroids and towards the planet, slowing down to establish an orbit with a force so small that not even a queen could notice it.

Sara established an orbit near the edge of the planet's sphere of influence, such that it would take nearly 100 of the planet's days to circle once. All the better to be farther away. All the better for a quick retreat. Some of the zerglings were overeager to explore it, but most of the crew wanted to stay back and examine it first. "Chemical readings, please" Sara said to the rest of her ship, specifically talking to engineering. They were already on top of it, exposing several wet, organic, sheets of varying colors, not unlike thinly sliced ham to the planet's light. These could be turned into spectrographs which would show the chemical composition of the atmosphere.

The engineers sent quiet communications between themselves as they looked at the sheets in disbelief before one announced to the rest of the ship. "Protoss!" At the sense of confusion she felt among the room she amended this cry, "or hybrids, I suppose." The entire ship became tense as an uncanny silence fell over it. "The Xel'Naga temple..." The readings had confirmed it but she wasn't too sure herself, it seemed beyond absurd. "The light we're seeing in the atmosphere is the kind of light we saw on Shakuras, or what remained of it, years after… the war. It's in much lower intensities than that light, but these are the same energy photons as that." Perhaps the Protoss had gotten to the planet first, or maybe the Terrans were actually Xel. It was a worrying thought—the idea that their awful creators were still around, but it would certainly explain Kerrigan's psionic strength, and the Zerg's hatred of them.

The whole situation looked bad, and slight feelings of regret spread throughout the hive, but Sora was not yet convinced. She asked the engineers what caused that light to emerge, to which a different one responded: "We're not entirely certain, because we have only recorded it twice, but we're pretty sure it's caused by the decay of cobalt-60. We haven't seen this chemical anywhere, except from these temples. They are mostly made of iron and when they are activated, they produce so much heat that they can cause spontaneous atomic fusion of airborne hydrogen gas into tritium, which in turn hits this iron turning it to cobalt and releasing a neutron."

"You haven't seen it _anywhere_," Sora pressed, "not even in terran _nukes_?" A few of the engineers shook their heads. "And you're sure that isn't just because we are not made of iron so there's nothing that can form into the cobalt?"

A third engineer shook his head in response to this question. "It's not just that we are not made of iron. If a terran wanted to create this material, it would need temperatures so hot it would require the force of a thousand nukes all at once. Nothing besides the Xel is capable of working with this much power." As the engineer said it, he knew he didn't believe his own words and neither did the rest of the ship. If there was one thing that could be said about terrans, they were certainly capable of making the impossible look normal. In any case, the crew set this issue to the side, after all, temples can only be used once a decade or less, and if one was activated there wouldn't be any terrans alive left on the planet. The small hive aboard Sora would not learn the truth of this cobalt until reconnecting with the rest of their species.

* * *

Falling from space was always exhilarating, but today was especially intense for Jonah. As he descended into the clouds, he fully expected to spot a giant military base through his pod, ready to slaughter him and the others who came with him. He was half-correct. There was certainly a forest of cement and steel below him, but it had been heavily corroded, and it was covered in a green slime. It also seemed bereft of terrans. Maybe the engineers were right about the hybrids having returned. It certainly could have been hybrid creep. Creep can only effectively generate energy from blue and cyan light anyway, so it would be just as effective if it were red or green as black. The deep purple color under Kerrigan's rule was chosen only for its effectiveness in hiding, a useful trait in combat. Most creep nowadays, including that which made up Sora, and Jonah's pod was a dim red, as it was aesthetically pleasing.

Jonah was relieved when he, his compatriots, or perhaps the pod itself (one could never be quite so sure), made the discovery that the green was not in fact a slime at all, but grasses! The Zerg knew about plants, but they also thought of them as exclusive to Zerus (and anywhere they had been intentionally transplanted from Zerus). Besides this, these structures were thick, tall, and woody, and looked nothing like the ones there. On Zerus, one was never more than a kilometer from a body of water on that planet, and because of it, plants there resembled mosses or ferns and relied on water for reproduction. Furthermore, nothing there was capable of producing wood.

It is hypothesized, but not proven by any zerg, that Zerus' plants could not develop wood naturally without having evolved away from water based reproduction. To explain why, it's important to understand that plants have two life-states, sporophytes and gametophytes. Sporophytes produce airborne spores which grow into gametophytes upon landing that reproduce with each-other to create the next generation of sporophytes. Gametophytes are short and live short lives. Their only goal is to reproduce quickly, and they use waterborne gametes to do so. A forest canopy would block the water and light that these short plants need to survive. The hypothesis goes that if Zerus' plants grew wood, they would grow so large as to steal resources like light and water from the next generation, making wood growth a deleterious or negative trait. In essence wood requires internal fertilization, and internal fertilization requires lack of water. If only they had artificial selection—they would benefit from a biology team or someone like Abathur.

The pod landed, spewing a bit of creep onto the rubble, careful to not touch any of the plants lest they hurt them. The explorers paid no such caution, too excited by the unique adaptations. With shocking precision a zergling scientist clawed a thin slice of the grass and handed it off to a mutalisk to ferry it back to Sora. The creatures were curious about where it got its carbon from. After digging up a few more blades of grass, Jonah thought it might have been through the soil. After all, the atmosphere had basically no carbon. Plants on Zerus used CO2 from the atmosphere, which made sense as that gas constituted 1% of their atmosphere (or about 10000 parts per million). In the atmospheric survey that the crew ran before landing, the gas seemed to be in concentrations of just 250PPM. With 1/40th the available carbon in the air, it seemed reasonable to assume that plants would have evolved some way to absorb it from the ground. Still, it's important to test your hypothesis so Jonah handed the grass he dug up to the mutalisk.

* * *

Meanwhile, on the leviathan, several of the scientists had just completed their DNA analysis of the plants. "Wavelet analysis of the genome reveals a peak signal to noise ratio of… 21?!" Alec looked shocked, but the results were undeniable. His mental alarm attracted the attention of the others, who immediately assumed that a mistake had to have been made in the DNA analysis. 21 decibels simply seemed far too low for these plants to stably survive. Zerg creatures were considered unstable if they had any less than a PSNR of 80 decibels. Because it was on a decibel scale, and because of the way the wavelet decomposition formula worked, 80 represented DNA that was either 1 million times more information dense, or 1 million times more resilient to mutations than these plants. (Or in the case of the Zerg, some combination of these). No mistake was found—neither in sequencing nor in the transformation of data. This plant was, in fact, quite surprisingly stable.

The next question on everyone's minds was the similarity analysis. "Uh, so this is weird. We have identified 1.3 or so million valid genes across all the cells we analyzed. But the genome as a whole only has 14,218 valid coding regions, as does each individual cell." What was going on here? For a few moments it was a mystery to the hive. But the clue was in the PSNR value that had been observed before. For this creature to have so many genes, it would need to have generated them during its development in areas that are especially sensitive to mutations. It would have to intentionally corrupt its genome in some of its cells to generate new genes. Why self corrupt? To answer that, the creatures needed to do a protein functionality analysis. Essentially through transcribing small samples of the DNA, the Zerg could figure out where the proteins these genes would end up.

The myriad of proteins which were coded by these few cells seemed to have no discernable purpose. In fact, many of them were likely uncoded at all. Those that were often ended up inside the plant's phloem where they obstructed, rather than benefitted, the transportation of nutrients. Although many of the Zerg suspected something was wrong, they were not sure what, nor what 'right' should look like, given that their only prior exposure to terran creatures were the humans themselves, and any records of their genetics, proteins, biological weaknesses, and so on, were scrubbed from the zerg's memory by Kerrigan the moment she took control (perhaps anticipating or fearing she might not control it forever). Their first hint came when one being, or maybe the whole ship all at once, observed a small invertebrate hiding among the grassy stalks they had brought onboard. A small grain moth was overwhelmed by the ship's high amounts of carbon dioxide (40 times that of Earth) and barely conscious and unable to react as the ship itself (the creep on the floor) held it down and plucked a single scale off its wings.

With this scale, the zerg were able to run the same tests. "2.5… decibels," Alec proclaimed. This caught the attention of the entire ship, and the creature became an object of fascination when Alec followed up with: "Well actually -0.3 decibels when you don't ignore the massive chunks of quickly mutating non-coding material. Anyway, this creature has a more reasonable number of genes, only about 9,326 unique ones with about 9120 in a given cell." There's no way such a creature could exist—it seemingly had more noise than signal. Even if it could somehow exist, with such a low PSNR, mutations would likely kill it in a few years at most.

Sora had gotten quite invested in the conversations of her scientists. "Maybe we should tell the creature," boomed her voice in Alec's mind. "Maybe it would appreciate the information. I'm gonna do an MFM analysis." Waves of neural activity echoed through the ship as its creep started examining the genome in depth.

A minimum fatal mutation number (or MFM) analysis was complicated to run, and took a large amount of brainpower and time to fully complete, but it had a lot of shortcuts Sora could take advantage of. Traditionally, you would need to examine the effects of mutations across the full genome of each cell specialization, a problem that had been reduced to a complexity of O(n^2 * m), where m is the number of specializations and n the genome size. This meant that doubling the number of base pairs quadrupled the problem difficulty. However, by looking at a random 2-3% of the genome and a random 5-10% of the cell specializations, you could find a maximum mfm value, which would be the true mfm value about 90% of the time. This simplified the problem by more than ten thousand times and made them solvable in minutes rather than months.

Meanwhile, Sora tried to get into contact with the creatures. The plant shavings may at one point have produced mental waves but it was severed from its source and quite dead. The moth, on the other hand, was barely conscious as the zerg scientists rushed to build something for it to breathe properly. It seemed confused about its situation and surroundings. This state was not helped by Sora asking it outright how it was still alive. It looked around at the pulsating creep and distant, blurry spiked titans, the ship's light insufficient for its eyes to build a clear image. The creature lazily responded that it wasn't sure what Sora meant.

At this point the MFM test had completed. Sora informed Alec, and the other scientists, and then the moth, that it had an MFM of 2 or less, and an MMC (minimum mutated cells) of 1, meaning 2 mutations across any of its specialized cells could be fatal to the moth. This was in the sense of cancer, or autoimmune disease, fewer mutations could kill the cell, but cells, unlike organisms, are replaceable. MFM was often related to PSNR. With a PSNR of 80, a zerg would likely have an MFM of around 18, and an MMC of at least 4. This means that at least 18 mutations would have to occur in four different cells for the creature to die, without any of these mutations getting detected. Increasing either MFM or MMC by even 1 exponentially decreases the chance of this happening. The chance for a zerg to die due to mutations is so small that if every atom in the visible universe was a zerg creature, it would take hundreds of trillions of years for even one of those creatures to succumb. The moth shrugged all this off, expressing that if it died, it died, and really it just wanted a mate.

Sora couldn't understand its urges, and neither could the other zerg, who had just built a little bubble for the moth. The bubble's walls were made from a similar material to the overlord's air sacs, but thin enough for it to be transparent and light enough for the moth to easily push it around like a hamster ball. However, they infused it with some of the proteins taken from the plant. Having discovered that the plant did indeed get its carbon from the air, it did so using specialized proteins that allowed for the buildup of CO2 into specialized cells in the bubble's walls and its conversion into oxygen and glucose. By placing them on the inside, they drew CO2 out of the moth's chamber, creating for it a much less toxic atmosphere. With this contraption complete and placed around the moth, it gained a burst of energy, and fear, as it tumbled around the ship aimlessly exploring. Sora probed its thoughts as it had since become a curiosity for the crew.

Once the moth calmed down, someone onboard asked it if it was aware of any other collective consciousnesses like the Zerg had. It said no, best it could tell the only organization of creatures it knew of were in a wasp's nest it had fended off as a larvae and flew by as an adult. Sora thanked the moth, and the crew eventually did collect DNA from such a creature, a paper wasp. Even though these were capable of organizing into a hive, they were far unlike zerg societies. Firstly, because they had similar PSNR values to the moth. Second, and more importantly, because they were separate beings who only helped each other as a result of being nearly genetically identical—any difference in appearance happening during development. Zerg, meanwhile, constituted of hundreds of species, all which acted and thought of themselves as a single organism. In an ironic twist, despite being superior by nearly all metrics, hives of such diversity as zerg would likely not evolve from this structure.

Even within an individual species, behaviors that are good for a species as a whole, but not individuals are often selected against. Consider a mutation that reduces the individuals one gives birth to by 1, but helps three distantly related members of a species give birth to an additional baby. If this mutation arises in a member, then the individuals who are benefited by it are very likely not going to have it, thus dooming the mutation to extinction. If every member of a population has this mutation, except one member, that member will gain the benefit of others without returning anything and will thus reproduce more on average, and will, over time, take over and cause this mutation to be eliminated from the gene pool. For hives, individuals are often quite closely related to each other—sisters who are 66% or more related. If a mutation arises that reduces the individuals one gives birth to by 1 but helps a sister or mother give birth to three more offspring, it will be selected for. If such a mutation arises in a mother, then two thirds of her children would have it as well. From the trait's perspective, helping three sisters reproduce, two of whom share the trait, is as beneficial to it spreading as you reproducing twice. In either case it creates the same number of children who could potentially have the trait. Ergo, hives can only occur among close family members within a single species.

In short, the zerg aboard were not especially impressed with how life had evolved on Earth, disappointed by the lack of a true unified hive. The scientists on the ground were packing up, ready to leave with a few other insect samples and declare Earth useless. Jonah wasn't so sure though. He had spotted a large stand of forest a little ways North of their landing zone. Expressing his interest to the other ground scientists created enough curiosity in the group to explore it. After all, they had spent a long time coming here and anything that would make this planet worth it should be investigated. Trekking a mile north, the creatures found themselves in a forest of Aspen.

Like the grass they had examined earlier, the trees that grew in this forest actually impressed the groundlings. Although the aspens too had a low PSNR (of 4, with a similar protein count to the moth), they were different from the animal hives. The sprouts were not family to each other, they were all small pieces of a single individual. Each tree genetically identical to every other one, and connected at the roots. They formed a symbiosis with a second species, a group of fungi which infiltrated the roots of this plant, trading information and resources. The scientists held a silent admiration for the giant beast that was the plant and fungi together—it wasn't a bunch of individuals working together as part of a family unit, it was a single being, a single individual, made up of multiple species so tightly connected in thoughts and supplies. The creatures saw themselves in it.

They took a few samples of the tree and its fungi and gathered around, waiting to ascend back to the ship, and that was that. As they waited they reflected on the tree and how it had somehow managed to evolve something most zerg thought only possible through artificial selection. For a brief moment, one of the scientists considered the possibility of destroying the plant and stopping its growth lest it become a new competitor. Although not a serious consideration, Jonah was quick to strike it down. "It's very well possible that one day, the stuff here will be able to ascend just as we did from Zerus many years ago. And when this happens it may compete with us, and in return let's welcome it. The universe is a lonely place, and it would be nice to have another creature in it that functions as we do." Others echoed this sentiment and whatever idea of extermination that may have emerged was quickly erased from their minds. Like it or not, the zerg creatures had the Terran humans on their mind. If they destroyed this plant, then these apes would be the only thing to ever come out of it. Perhaps, as with the Zerg and Protoss, alien civilizations always came in pairs.

* * *

Half a mile Southwest, hiding within the ruins of the old world, a single human perched himself. Lee was a young man in his 20s, wearing a tattered jumpsuit that once read "UED Shelter 29." It had since been plastered over with many layers of chlorophyll and charcoal and all kinds of other natural paints as camouflages. Lee's hair was shaved to a quarter inch thick, as was his beard which grew thick through his face. He had a backpack, in which he kept some pistol ammunition, a bag of granola, a handmade water filter out of charcoal, a sleeping bag, and a crank operated battery charger. On his belt, an M1911 pistol and battery operated walkie talkie. He reached for the device multiple times but decided against it, unsure if the aliens could sniff out the wavelengths of light it used.

As he watched the aliens slicing the grass, he wanted to scream into it, or at them. For how much of an aversion the aliens seemed to have with the human structures they stepped around, they seemed to instantly fall in love with human inventions. For the plant they had grabbed was Wheatie 12, a synthetic grain created to replace millet and wheat after a virus killed them off. The entire genome was human assembled from other existing lifeforms. The photosynthetic pathways taken from other grasses, the active immune system from mammals, and a set of hormones from insects. After the collapse, and the bombs, it had spread from the many farmlands to every shrubland and savanna, often outcompeting existing grasses as it had very simple nutrient requirements, and a propensity to grow quickly when it met them. _Maybe that was why the aliens were so attracted to it, maybe because it was artificial_, the human quietly thought.

When the creatures headed North, Lee used the opportunity to rush back to his town, Needles of what was once California. When he approached the entrance, a woman he recognized greeted him from a three story watchtower. She exclaimed: "Did you see em? The aliens!" He nodded, realizing that dozens of townsfolks, as many as could fit, were all gathered in the watchtower, trading turns on the telescope. "Our leader wanted to tail em, figures it's the only useful thing we can do with the vessel we built. Look—we all want an excuse to get off this god forsaken planet but we're gonna be generous and offer the opportunity to you since you got closer to them and are probably more familiar with em." Lee recognized the obvious lie, but wanted away from the town just as much as they wanted him gone. He filled his waterskin at the well and then rushed to the vessel.

A protoss interceptor sat at the middle of a metal pad made of scraps of sheet. The engines and half the hull were still made of original Protoss parts salvaged from the remains of some battle many years ago. The rest of it was welded together diligently by the townsfolk. Nobody in the town knew where the original vessel came from, nor the aliens who made it. The man opened the ship's door, a metal hatch that seemed more fitting for a World War 2 tank. The inside had been retrofitted to barely fit a single person. It had been stocked with a few tanks of oxygen (in case of leaks), water, and food, all in arms reach of the pilot seat—a hard wood desk chair attached to a metal gyroscope. The man tried not to think about the possibility of the tanks exploding as he sat down and turned on the computer, a single 15 inch display panel that had to be two centuries old lit up. With the computer on, he could hear outside his ship. The others were outside, urging him to "hurry up and leave already."

_Fine_, Lee thought, and activated the engines. They sputtered for a moment as the vessel's batteries were low; the townsfolk having kept it inside or in the shade. Eventually though, they managed to come on, and generate enough thrust to overcome gravity. He flew directly upwards, holding one hand on the bottom of his chair to keep himself from falling. The town below disappeared into haze and clouds and the stars above grew as clear as nighttime as Lee left the atmosphere. Switching the display to show electromagnetic signals, he quickly located the leviathan and silently accelerated towards it.

After human infighting caused the UED to collapse and lead to the world blowing itself up with neutron bombs, the remaining human survivors affectionately referred to their species as a pest animal. The comparison wasn't entirely inaccurate; man had grown to conquer much of Earth and her resources in a hundred generations. But it was also accurate in another way. No matter what anyone did, it was nearly impossible to fully eradicate homo sapiens. Not the brood wars, nor climate change, nor nuclear winter could put an end to this tenacious animal. And for good reason: Give a human a single nook or cranny and it will find a way to slip in and preserve itself. Lee pondered this as he slowly docked with the leviathan, using a hook on the ship, he attached himself gingerly to one of the exterior pieces of chitin. So delicate was he, that the zerg creatures inside didn't notice as they took off into hyperspace and back to their home world carrying a small pest.


End file.
